It has been known that fader controls are grouped and interlocked with each other in a conventional mixer, so that the grouped state can be easily recognized visually and also a setting operation can be easily performed. In this case, fader controls of respective channels are provided, and a plurality of fader controls are grouped, allowing operating the fader controls in the same group in an interlocked manner by operating a fader control of a group master. Further, a window of a particular group is opened in response to a selecting operation by the user on a display screen, and images indicating the setting states as for respective fader controls belonging to the particular group are displayed on the window. In response to the user's operation on the images indicating the setting states of the respective fader controls belonging to the particular group, which are displayed on the window of the particular group, changing the setting state of each fader control belonging to the particular group has been conventionally performed (see PTL1).
Specifically, when performance sounds by a large musical instrument such as a drum set or a grand piano, or by a large number of people such as a chorus or strings (string orchestra) are collected, a plurality of microphones are set and their inputs are sent to a mixer, and a volume balance is achieved through the mixer. The volume balance is adjusted by operating fader controls of channels of the mixer which receives inputs from the microphones and/or the like. However, after achieving the balance, it is necessary to operate the fader controls of all associated channels at the same ratio in order to increase or decrease the total volume of target sound sources thereof. Accordingly, a “fader group processing” to assign desired associated channels to one group through is provided, enabling to collectively control the volumes of all channels belonging to the one group at the same ratio in an interlocked manner with a predetermined group master fader control provided in correspondence with the one group. Thus, the volume of the group can be controlled uniformly without losing the volume balance among the set group channels. That is, without losing sound field feelings or sound tones formed by the microphone setting, the volumes of parts of a drum, a piano, and so on can be controlled in an interlocked manner. This group is called a DCA group for example in the mixer.